Magnetoelectric composites of 0.6(Ni0.7Zn0.3Fe2O4) / 0.4((Na, Li, Sr)NbO3 + MnO2) are prepared by conventional ceramic technology. The effect of composite sintering temperature on their phase composition and structure is studied. It is stated that the composites obtained are two phase systems (perovskite and spinel). It is established that modulation of spinel structure is shown more accurately at low sintering temperatures (1180 °C), while modulation of perovskite structure is shown at high temperatures (1220 °C). The discovered modulations of perovskite and spinel structures are assumed be connected with extended defects such as crystallographic shear planes. Increasing composite sintering temperature (Tsint.≥1200 °C) was shown to lead to the disappearance of an impurity phase and the change of perovskite phase composition.